Virtual (virtual), virtual (virtual)

Virtual (virtual), virtual (virtual)

Virtual)

Virtual keywords are used to modify methods, properties, indexers, or event declarations, and allow them to be rewritten in a derived class.

Read a piece of code:

UsingSystem;

Class

{

PublicVoidF()

{

Console.WriteLine("A.F ");

}

}

Class B:

{

PublicNewVoidF() // Note the new Keyword

{

Console.WriteLine("B. F ");

}

}

Class Test

{

Static voidMain()

{

B B =NewB();

A a = B;

A.F();

B.F();

}

}

Output: A.F

B. F

If the above Code is in memory:

 

 

 

 

 

Let's look at another piece of code:

UsingSystem;

Class

{

PublicVirtual voidF()

{

Console.WriteLine("A.F ");

}

}

Class B:

{

PublicOverride voidF()

{

Console.WriteLine("B. F ");

}

}

Class C: B

{

PublicNewVoidF()

{

Console.WriteLine("C. F ");

}

}

Class Test

{

Static voidMain()

{

C c =NewC();

A a = c;

A.F();

}

}

Output: B. F

-> The member of the base class searches for the inheritance chain, finds the member before the new modifier, and calls the member.

Polymorphism ):

Polymorphism refers to the ability of two or more objects of different classes to make different responses to the same message.

-> Virtual and override keywords: Polymorphism provides a method for subclass to customize how to implement the methods defined by the base class;

See the following code:

UsingSystem;

Class Employee

{

ProtectedString _ name;

PublicEmployee(){}

PublicEmployee(String name)

{

_ Name = name;

}

PublicVirtual voidStartWork()

{

Console.WriteLine(_ Name + "start as work ");

}

}

Class Manager: Employee

{

PublicManager(String name ):Base(Name ){}

PublicOverride voidStartWork()

{

Base.StartWork(); // Pay attention to the usage of base

Console.WriteLine("Issue a task ");

}

}

Class Seller: Employee

{

PublicSeller(String name ):Base(Name ){}

PublicOverride voidStartWork()

{

Base.StartWork();

Console.WriteLine("Sales product ");

}

}

Class Test

{

Static voidMain()

{

Employee [] emp =NewEmployee [2];

Emp [0] =NewManager("James ");

Emp [1] =NewSeller("Li Si ");

Foreach(Employee eInEmp)

{

E.StartWork();

}

}

}